The static friction force on a rod immersed in granular matter
颗粒物质中圆棒受到的静摩擦力

The dependence of the static friction force exerted on a rod immersed in granular matter on the filling height of granules and the diameter of the rod is studied experimentally. It is observed that the friction force increases with the filling height of granules and increasing diameter of the rod. A model based on the continuous media is given, which can explain the observed results. It is demonstrated that the friction force is proportional to the diameter of the rod and the square of the filling height in the case of shallow granules, while it is a linear function of the filling height in the case of very deep granules,i.e. the friction force is proportional to the area of the interface between the rod and granules.